Method of using multiple received satellite signals to compensate satellite multipath estimation error

Abstract

The present invention provides a receiver including an RF circuit, a correlator and a signal delay estimator. The RF circuit is configured to receive a first satellite signal and a second satellite signal to generate a first base-band signal and a second base-band signal, respectively. The correlator is configured to use a first local signal to integrate with the first base-band signal to generate a first correlation result, and to use a second local signal to integrate with the second base-band signal to generate a second correlation result. The signal delay estimator is coupled to the correlator, and is configured to use the second correlation result to compensate the first correlation result to generate a compensated first correlation result, and determine a signal delay of the first satellite signal according to the compensated first correlation result.

What is claimed is: 
     
       1. A receiver, comprising:
 an radio-frequency (RF) circuit, configured to receive a first satellite signal and a second satellite signal to generate a first base-band signal and a second base-band signal, respectively, 
 a correlator, configured to use a first local signal to integrate with the first base-band signal to generate a first correlation result, and to use a second local signal to integrate with the second base-band signal to generate a second correlation result; 
 a signal delay estimator, coupled to the correlator, configured to use the second correlation result to compensate the first correlation result to generate a compensated first correlation result, and determine a signal delay of the first satellite signal according to the compensated first correlation result. 
 
     
     
       2. The receiver of  claim 1 , wherein an Auto-Correlation-Function (ACF) of the first satellite signal is different from the ACF of the second satellite signal. 
     
     
       3. The receiver of  claim 2 , wherein the ACF of the first satellite signal is wider than the ACF of the second satellite signal. 
     
     
       4. The receiver of  claim 2 , wherein the first satellite signal and the second satellite signal are from a same satellite of a satellite system, and the satellite system comprises one of a Global Positioning System (GPS), a Quasi Zenith Satellite System (QZSS), a Galileo satellite navigation system, a BeiDou satellite navigation system, a GLONASS system, an Indian Regional Navigation Satellite System (NavIC) and a Satellite-Based Augmentation System (SBAS). 
     
     
       5. The receiver of  claim 2 , wherein the first correlation result is a composite ACF comprising a first ACF corresponding to a direct path of the first satellite signal and a second ACF corresponding to a reflected path of the first satellite signal, and the second correlation result comprises a third ACF corresponding to a direct path of the second satellite signal and a fourth ACF corresponding to a reflected path of the second satellite signal; and the signal delay estimator predicts the second ACF according to the fourth ACF, and uses the predicted second ACF to compensate the composite ACF to obtain the compensated first correlation result. 
     
     
       6. The receiver of  claim 2 , wherein the first correlation result comprises m sample points of the ACF corresponding to the first satellite signal, and the second correlation result comprises n sample points of the ACF corresponding to the second satellite signal, and the signal delay estimator uses the relationship among the ACF of the first satellite signal, the ACF of the second satellite signal, the m sample points of the ACF of the first satellite and then sample points of the ACF of the second satellite signal, to compensate values of the m sample points of the first satellite signal. 
     
     
       7. The receiver of  claim 6 , wherein m is equal to two, and n is equal to one. 
     
     
       8. The receiver of  claim 6 , where the first correlation result comprises two sample points of the ACF of the first satellite signal corresponding to early and late local signal replica of the first satellite signal, which are used to track the direct path of the first satellite signal. 
     
     
       9. The receiver of  claim 6 , where the first correlation result comprises one sample point of ACF of the first satellite signal corresponding to prompt local signal replica of the first satellite signal, which is used to track and/or decode the direct path of the first satellite signal. 
     
     
       10. The receiver of  claim 6 , where the second correlation result comprises one sample point of the ACF of the second satellite signal, which is used to search possible reflected path of the second satellite signal. 
     
     
       11. The receiver of  claim 6 , where the first correlation result comprises one sample point of the ACF of the first satellite signal corresponding to prompt local signal replica of the first satellite signal, and the second correlation result comprises two sample points of the second satellite ACF corresponding to the prompt local signal replica of the direct and reflected path respectively. 
     
     
       12. The receiver of  claim 2 , wherein the first correlation result is a composite ACF comprising an early code and a late code correlation of a first ACF corresponding to a direct path of the first satellite signal and a second ACF corresponding to a reflected path of the first satellite signal, and the second correlation result comprises an early code and a late code correlation of a third ACF corresponding to a direct path of the second satellite signal, and an early code and a late code of a fourth ACF corresponding to a reflected path of the second satellite signal; and the signal delay estimator predicts the second ACF according to the early code and the late code of the third ACF and the early code and the late code of the fourth ACF, and uses the predicted second ACF to compensate the composite ACF to obtain the compensated first correlation result. 
     
     
       13. The receiver of  claim 12 , wherein the signal delay estimator uses the predicted second ACF to compensate at least one of the early code and the late code of a first ACF to obtain the compensated first correlation result. 
     
     
       14. A signal processing method, comprising:
 receiving a first satellite signal and a second satellite signal to generate a first base-band signal and a second base-band signal, respectively; 
 using a first local signal to integrate with the first base-band signal to generate a first correlation result; 
 using a second local signal to integrate with the second base-band signal to generate a second correlation result; and 
 using the second correlation result to compensate the first correlation result to generate a compensated first correlation result, and determining a signal delay of the first satellite signal according to the compensated first correlation result. 
 
     
     
       15. The signal processing method of  claim 14 , wherein an Auto-Correlation-Function (ACF) of the first satellite signal is different from the ACF of the second satellite signal. 
     
     
       16. The signal processing method of  claim 15 , wherein the ACF of the first satellite signal is wider than the ACF of the second satellite signal. 
     
     
       17. The signal processing method of  claim 15 , wherein the first satellite signal and the second satellite signal are from a same satellite of a satellite system, and the satellite system comprises one of a Global Positioning System (GPS), a Quasi Zenith Satellite System (QZSS), a Galileo satellite navigation system, a BeiDou satellite navigation system, a GLONASS system, an Indian Regional Navigation Satellite System (NavIC) and a Satellite-Based Augmentation System (SBAS). 
     
     
       18. The signal processing method of  claim 15 , wherein the first correlation result is a composite ACF comprising a first ACF corresponding to a direct path of the first satellite signal and a second ACF corresponding to a reflected path of the first satellite signal, and the second correlation result comprises a third ACF corresponding to a direct path of the second satellite signal and a fourth ACF corresponding to a reflected path of the second satellite signal; and the step of using the second correlation result to compensate the first correlation result to generate the compensated first correlation result comprises: predicting the second ACF according to the fourth ACF, and using the predicted second ACF to compensate the composite ACF to obtain the compensated first correlation result. 
     
     
       19. The signal processing method of  claim 15 , wherein the first correlation result comprises m sample points of the ACF corresponding to the first satellite signal, and the second correlation result comprises n sample points of the ACF corresponding to the second satellite signal, and the signal processing method further comprises:
 using the relationship among the ACF of the first satellite signal, the ACF of the second satellite signal, the m sample points of the ACF of the first satellite and the n sample points of the ACF of the second satellite signal, to compensate values of the m sample points of the first satellite signal. 
 
     
     
       20. The signal processing method of  claim 19 , wherein m is equal to two, and n is equal to one. 
     
     
       21. The signal processing method of  claim 19 , where the first correlation result comprises two sample points of the ACF of the first satellite signal corresponding to early and late local signal replica of the first satellite signal, which are used to track the direct path of the first satellite signal. 
     
     
       22. The signal processing method of  claim 19 , where the first correlation result comprises one sample point of ACF of the first satellite signal corresponding to prompt local signal replica of the first satellite signal, which is used to track and/or decode the direct path of the first satellite signal. 
     
     
       23. The signal processing method of  claim 19 , where the second correlation result comprises one sample point of the ACF of the second satellite signal, which is used to search possible reflected path of the second satellite signal. 
     
     
       24. The signal processing method of  claim 19 , where the first correlation result comprises one sample point of the ACF of the first satellite signal corresponding to prompt local signal replica of the first satellite signal, and the second correlation result comprises two sample points of the second satellite ACF corresponding to the prompt local signal replica of the direct and reflected path respectively. 
     
     
       25. The signal processing method of  claim 15 , wherein the first correlation result is a composite ACF comprising an early code and a late code correlation of a first ACF corresponding to a direct path of the first satellite signal and a second ACF corresponding to a reflected path of the first satellite signal, and the second correlation result comprises an early code and a late code correlation of a third ACF corresponding to a direct path of the second satellite signal, and an early code and a late code of a fourth ACF corresponding to a reflected path of the second satellite signal; and the step of using the second correlation result to compensate the first correlation result to generate the compensated first correlation result comprises:
 predicting the second ACF according to the early code and the late code of the third ACF and the early code and the late code of the fourth ACF, and using the predicted second ACF to compensate the composite ACF to obtain the compensated first correlation result. 
 
     
     
       26. The signal processing method of  claim 25 , wherein the step of using the predicted second ACF to compensate the composite ACF to obtain the compensated first correlation result comprises:
 using the predicted second ACF to compensate at least one of the early code and the late code of a first ACF to obtain the compensated first correlation result.